Mamoru heads to Crown Arcade, where Motoki and his friend Endo are heading inside. Motoki identifies Mamoru as "Usagi's friend" and thinks that Mamoru is the new part-timer. Motoki sends Endo inside, but Mamoru uses his powers to make Endo disappear and hypnotize Motoki into thinking Mamoru is Endo. A woman named Reika walks into the Arcade to give Motoki the book he left in class. She sees Mamoru, but is surprised when Motoki calls him Endo. Reika drops her book on semiprecious stones, and begins talking to Mamoru about the stones kunzite, zoicite, nephrite, and jadeite. Mamoru tells her he has the exact four stones.

The girls decide to hold a meeting at Ami's place. Usagi calls Rei from her fire reading, and when Rei comes outside of the temple she sees shadows in the fire of the sun, which is a bad sign just like the results of her reading. It could possibly mean that the odds are against the senshi in the next battle.

The girls enter Ami's penthouse building; Minako drops the sword and leaves a scratch on the marble entrance. Ami takes them inside and gives Minako a diamond ring to tap the sword with. The diamond (which is the hardest substance in the world) cracks. Ami says she analyzed the stone and a piece of pillar from the moon. Both are either made of or formed into a poisonous stone. Around this point, Usagi falls asleep on the couch. Makoto picks up Usagi and puts her in the bedroom. The discussion continues, and Usagi wakes up in an upset mood, reminiscing about waking up in Mamoru's bed and seeing the sunset from his room. Usagi decudes to sneak out and go play the Sailor V game. When she walks inside the arcade, she sees Mamoru playing the Sailor V game. Mamoru touches Usagi's odango and says that it reminds him of Sailor Moon. Motoki introduces him as Endo, and Mamoru lets Usagi play the Sailor V Game.

Minako's pen beeps during the meeting, and Minako feels that someone is playing the Sailor V game at an incredible rate. She sees Usagi is missing, so the girls head off to the Arcade. They see Mamoru in the Arcade, but Rei senses that he isn't Mamoru and they must keep Usagi away from him.

Usagi avoids walking home with Naru, and spends all her time at the Arcade. Luna warns her, but Usagi still can't help but go to see Mamoru. Mamoru brings up Usagi's resemblance to Sailor Moon again, and asks where Sailor Moon and Sailor V's control room is. Usagi decides to leave, but Mamoru tells her to come again and that he wants to know her secrets. He tries to cast a spell on her, but it doesn't work.

The next day, Reika sees Motoki and "Endo" walking together again. Ami and Rei ask if she knows about Endo, and Reika tells them that the Endo she knows is a geeky boy with thick glasses. Makoto confronts Mamoru and Motoki alone about what they're doing to Usagi, and Mamoru casts a spell on her.

Makoto calls an emergency meeting in the control room to tell Usagi that "Endo" is the enemy and he wants the princess and the crystal. The intruder alarm goes off, and Makoto's spell snaps into action. She tries to snatch the ginzuishou from Usagi's neck, but Minako intercepts and kicks Makoto to the floor. Tuxedo Kamen and Motoki enter the control room, so Minako transforms and yells, "Sailor V Kick!" as she kicks Motoki to the floor. Then she takes the Whip of Love and uses her Venus Love-Me Chain attack on Motoki. She grabs the crystal, but Kamen blasts at her until she lets it go. He gets the crystal, and Luna tells Usagi to transform and fight. Luna bites Kamen's shoulder, and he flings her across the room where she collides and falls down, lying in a pool of her own blood. Usagi transforms and uses Moon Healing Escalation to heal Luna and Makoto. She tries to blast Kamen but Queen Beryl appears behind him. Beryl reveals that this evil Kamen is really Endymion.

After a short skirmish, Kamen begins blasting again. Mercury and Jupiter grab unconscious Motoki and teleport outside. Motoki wakes up and recognizes Ami and Makoto as they teleport back. Mercury creates a shield to protect the area by yelling, "Hyperspace Area Formation!" Beryl uses her long hair to grab hold of Moon. She then reveals the existence of the great leader Queen Metallia, born from a dark spot in the sun. Venus remembers Beryl killing Prince Endymion and killing Beryl with a sword. Venus uses her Venus Love-Me Chain attack on Beryl, but it fails, and she is thrown back. Venus calls upon the sword from the moon, but Jupiter grabs it and uses it to cut the hair gripping Moon. The hair tries to strangle Moon, but she doesn't want to die without saving Kamen. Venus stabs Beryl, and the sword lights up. As Beryl crumbles and dies, she reveals that all she wanted wasn't invincibility or immortality like she said before, but to have Endymion all to herself. Venus reads an engraving on the sword that says whe the sword lights up, the ginzuishou follows the princess' heart and to bring peace, service must be given to the moon's holy tower, and the Great Power of the moon must be released. Luna reveals that this is the method of sealing needed to seal away evil. Venus faints, and Kamen grabs her and the sword and runs through a warphole. Moon follows them, but the warp shuts before anyone else can follow.

The senshi use the control room equipment to track them to the north pole. They teleport there and make their way to the dark castle. Inside the castle, Sailor Moon tries to make Kamen recognize her, but he lifts her by her neck and demands to know how to control the crystal and the Great Power of the moon. Moon reaches for the crystal, but she gets shot backward by its power. The other senshi enter as Queen Metallia appears and Kamen blasts again. Luna and Artemis teleport in, and Luna tells Moon that she must get the light from the crystal out of Kamen and into the ginzuishou to complete the sealing method. Mars uses Aku Ryo Tai San and Venus uses Rolling Heart Vibration, but nothing works. Moon uses Moon Healing Escalation but it doesn't work. Moon doesn't know what to do, and Kamen and the crytal react to the confusion in her heart. She picks up the sword and slashes Kamen across the chest. As his wounded body falls face-first, she leans up and kisses him. Then she stabs herself in the heart.